Introduction
The advent of GNSS, Global Navigation Satellite Systems has brought about an additional navigational aid for aircrafts. The presence of GNSS (specifically, Global Positioning System) receivers has become commonplace in the aircrafts of today. Due to their complementary error characteristic, approaches involving GPS coupled with the INS (Inertial Navigation System) are being looked into for complete navigation and attitude estimation of the aircraft.
Overview of Project
The work described below was done over a period of 8 months by Vaibhav Unhelkar under the guidance of Prof H Hablani. This section describes the overview of the project. The approach adopted, as described below, was due to pedagogical reasons.
Trajectory Estimation with On-Board GPS
Firstly, to appreciate the use of GPS in aircrafts, a simplified model of GPS on an aircraft was studied. For modelling purposes, the aircraft was assumed to be a point mass and hence INS was decoupled from the system. Further to understand how GPS data is processed, basics of Kalman Filtering were studied and an Position Velocity (PV) - Extended Kalman Filter (EKF) was designed for the above-mentioned model. Lastly, simulations were carried out in order to observe the performance of the EKF.
Navigation with Integrated GPS - INS
In order to incorporate the Inertial Navigation System in our simulations, basic models of the Navigation Error Equations were studied. Also, in order to understand GPS - INS integration various integration architectures, viz. loosely-coupled, tightly-coupled and deeply-coupled were studied. To develop upon the simulations carried out earlier, covariance analysis of a simplified GPS – INS EKF was carried out. Lastly, to carry out a detailed simulation for the GPS – INS integrated EKF, formulation was studied from (Rogers, 2007) and simulations were carried out.